External Resonator Research Articles

Carrier-envelope offset frequency measurement by means of an external optical resonator

A general-purpose method based on the implementation of the asymmetric Pound–Drever–Hall (PDH) technique is proposed to measure the carrier-envelope offset (CEO) frequency of a mode-locked laser using an external optical cavity. By analyzing the synchronously demodulated signal of the spectrally filtered cavity reflection when the optical resonator is locked to the mode-locked laser, a discriminating signal depending on the relative frequency offset between the mode-locked and optical cavity comb-like spectra is obtained. For a given geometry and group delay dispersion (GDD) of the cavity parameters (i.e., a known cavity mode offset), this signal can be used to retrieve the laser CEO. This approach turns out to be advantageous in terms of setup complexity with respect to other well-known techniques that rely on non-linear frequency generation, such as f–2f interferometers. In addition, this method can be used to precisely determine the laser–cavity spectral coupling, which is an important topic in cavity-enhanced spectroscopy and non-linear optics applications. After the theoretical description of the generalized asymmetric PDH signal, an experimental validation of the proposed method is reported using an Er-doped fiber frequency comb source centered at 1,550 nm, with a repetition rate of 250 MHz, locked to a linear optical cavity with a 1 GHz free spectral range. The theoretical effect of the GDD is confirmed experimentally using different cavity configurations. Moreover, the comparison with the CEO frequency values measured using an f–2f interferometer demonstrates the feasibility of the proposed method.

Stochastic resonance analysis of a coupled high-speed maglev vehicle-bridge coupled system under bounded noise

Coupled oscillations typically occur in maglev vehicle-bridge coupled systems excited by bounded noise caused by guideway irregularities. The paper employed Hamilton equations to derive the corresponding canonical transformation equations and determined the critical stable regions for two kinds of resonances using the largest Lyapunov exponents. The results show that the critical stable region between the excitation amplitude and the resonant frequency ratio is a valley shape when the system has external resonance only. When considering both internal and external resonances, the critical stable region between the excitation amplitude and resonant frequency ratio presents a small saddle shape. Energy transfers from the first to the second oscillator under with both internal and extrinsic resonance. As the guideway irregularities’ coefficients increase, the maximum Lyapunov exponents of the two conditions change from negative to positive, which means that the system varies from a stable state to instability.

Low‐Threshold, External‐Cavity‐Free Flexible Perovskite Lasers

AbstractA distinct advantage of halide perovskite semiconductors is their potential as gain media in high‐performance, all‐solution‐processed flexible lasers. However, most perovskite microlasers employ external optical resonators with rigid and high‐temperature/vaccum‐processed structures unsuitable for flexible applications. Here, low‐threshold, external‐cavity‐free perovskite lasers (≈550 nm, linewidth: ≈0.3 nm, quality factor: ≈1900, room temperature), prepared with excellent reproducibility using simple one‐step spin‐coating and low‐temperature annealing, are demonstrated. Exceptionally low lasing thresholds of 9.3 and 14.6 µJ cm−2 are achieved for external‐cavity‐free perovskite lasers on rigid and flexible substrates, respectively. The thresholds and quality factors are on par with that of high‐performance perovskite microlasers with well‐designed external cavities. The lasers exhibit good operational stability, showing half‐life of >1.8 × 108 pulses under optical pumping in air. Transient optical experiments reveal that the low thresholds stem from enhanced band‐to‐band spontaneous and stimulated emission processes in the high‐quality microcrystalline perovskite, effectively out‐pacing trap‐mediated and Auger processes detrimental to the lasing action. The flexible perovskite lasers retain >95% of the initial intensity after 10000 bending cycles, showing outstanding mechanical durability. As these lasers can be produced from solution within minutes at low costs, the findings are expected to enable high‐throughput, scalable fabrication of perovskite lasers for emerging applications.

Modeling and Control Method to Suppress Common-Mode Resonance Circulating Current for High-Power Parallel Three-Level Inverters System With Improved LCL Filter

In parallel three-level inverters, to eliminate the undesired internal common-mode (CM) resonance circulating currents (ICMRCCs) and external CM resonance circulating currents (ECMRCCs) introduced by the improved <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> , the inverter-side CM current feedback (ICMCF) control is presented. However, since the switching frequency of the inverters is generally low in high-power applications to reduce power loss, the stability of the ICMCF control will be threatened by the delays of digital controller. In this case, the existing methods are not capable of ICMRCC and ECMRCC suppression any more. To deal with the situation, an improved CM resonance circulating current control method for high-power parallel inverters is proposed. First, the model of ICMCF with control delay is established. Second, the influences of control delay with different sampling modes on the stability of CM current control are investigated. Based on this, the allowable range of control delays and sampling frequency to keep the system stable is analyzed and deduced. Third, the multisampling mode is further extended to CM current control in the parallel inverters. The analysis results show that the stability margin and control bandwidth of the ICMCF control are significantly improved. Finally, the theoretical analysis and proposed control method are verified by simulation and experiment.

Nonlinear dynamics of a tubular beam considering distortion of the cross sections and internal resonances

The nonlinear dynamics of a thin tube under the action of a harmonic external load is addressed in the paper. Use is made of a beam-like model which extends the Timoshenko beam model with further kinematic descriptors, related to the change in shape of the cross section. The external load is applied in half cap of the pipe, directly triggering both the bending of the axis-line and the flattening of the cross sections. The equations of motion are projected on a reduced basis constituted by the first three linear modes, and then the solutions are sought via the multiple scale method, for two different external resonance conditions. Internal resonances among the modes are considered as well. The outcomes, compared with pure numerical solutions, highlight the possible energy exchange between local modes, i.e., those describing flattening and warping of the cross sections, and global modes, i.e., those related to bending of the axis-line and rotation of the cross section of the pipe.

Non-local scattering control in coupled resonator networks.

We demonstrate scattering control of Gaussian-like wave packets propagating with constant envelope velocity and invariant waist through coupled resonator optical waveguides (CROW) via an external resonator coupled to multiple sites of the CROW. We calculate the analytical reflectance and transmittance using standard scattering methods from waveguide quantum electrodynamics and show it is possible to approximate them for an external resonator detuned to the CROW. Our analytical and approximate results are in good agreement with numerical simulations. We engineer various configurations using an external resonator coupled to two sites of a CROW to show light trapping with effective exponential decay between the coupling sites, wave packet splitting into two pairs of identical Gaussian-like wave packets, and a non-local Mach-Zehnder interferometer.

Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes.

Squaraines are prototypical quadrupolar charge-transfer chromophores that have recently attracted much attention as building blocks for solution-processed photovoltaics, fluorescent probes with large two-photon absorption cross sections, and aggregates with large circular dichroism. Their optical properties are often rationalized in terms of phenomenological essential state models, considering the coupling of two zwitterionic excited states to a neutral ground state. As a result, optical transitions to the lowest S1 excited state are one-photon allowed, whereas the next higher S2 state can only be accessed by two-photon transitions. A further implication of these models is a substantial reduction of vibronic coupling to the ubiquitous high-frequency vinyl-stretching modes of organic materials. Here, we combine time-resolved vibrational spectroscopy, two-dimensional electronic spectroscopy, and quantum-chemical simulations to test and rationalize these predictions for nonaggregated molecules. We find small Huang-Rhys factors below 0.01 for the high-frequency, 1500 cm-1 modes in particular, as well as a noticeable reduction for those of lower frequency modes in general for the electronic S0 → S1 transition. The two-photon allowed state S2 is well separated energetically from S1 and has weak vibronic signatures as well. Thus, the resulting pronounced concentration of the oscillator strength in a narrow region relevant to the lowest electronic transition makes squaraines and their aggregates exceptionally interesting for strong and ultrastrong coupling of excitons to localized light modes in external resonators with chiral properties that can largely be controlled by the molecular architecture.

Wide Bandwidth Axial Ratio Circularly Polarized Array Antenna based on External Resonator

This study introduces a wide bandwidth and wide axial ratio (AR), circularly polarised (CP), patch array antenna. By combining dual layers of a polarizer with dual layers of linearly polarized microstrip patch antenna, a novel method is created for generating circular polarization waves with a wide frequency range. The dual-layer 2 × 2 and 2 × 8 microstrip patch array antenna is employed to achieve linearly polarized waves and the external polarizer consists of a 3 × 3 and 3 × 12 four-layer dual rings polarizer that transforms linearly polarized (LP) waves into CP waves. The |S11| −10 dB bandwidth of small and large-scale circular polarized array antennas is 20% and 27.06% at 5 GHz, respectively, Simulations and testing show that the 3-dB axial ratio bandwidth (ARBW) at 5 GHz is 17%. The suggested antenna has a lot of potential for satellite communication applications because of its easy structure, wide ARBW, and wide impedance bandwidth.

Spontaneous Raman spectra analysis and efficient nanosecond pulse Raman laser of a BaTeW2O9 crystal.

In this Letter, the spontaneous Raman spectra of a novel, to the best of our knowledge, crystal α-BaTeW2O9 (α-BTW) are characterized and analyzed. The relative Raman gain coefficient of the α-BTW crystal is calculated to be 0.84 times that of YVO4. With a 35-mm-long crystal, the first-order Raman laser of α-BTW operating at 1178 nm is realized. The simple external resonator setup is employed in the first-order Raman laser of α-BTW. The pump source is a lamp-pumped electric-optical Q switched Nd:YAG laser amplifier system operating at 1064 nm with a pulse width of 10 ns. The Raman laser exhibits a threshold of 14.7 MW/cm2. In our experiments, a maximum pulse energy of 21.5 mJ is obtained with an optical-to-optical conversion efficiency and slope efficiency of 43.6%, 57.9%, respectively. Due to its high laser damage threshold, relative high Raman gain coefficient, and excellent thermal properties, the α-BTW crystal is a potential Raman material.

Hybrid integrated ultralow-linewidth and fast-chirped laser for FMCW LiDAR.

Narrow linewidth and fast-chirped frequency are essential in frequency-modulated continuous-wave lasers. We introduce a laser that meets these requirements by coupling a distributed feedback laser with an external high-Q microring resonator, where a bulky stacked piezoelectric chip is attached to the resonator for fast tuning. The laser demonstrates an ultranarrow intrinsic linewidth of 22 Hz in the self-injection-locked state. Actuated by the bulky piezoelectric chip, the maximum triangular actuation bandwidth can reach 100 kHz. The driving voltage is filtered to avoid a resonant mechanical mode, obtaining the minimum residual linearity error at 10 kHz with a 4.2 GHz tuning range. A light detection and ranging system was set up for a proof-of-concept experiment, demonstrating a high detection precision with standard deviations of 2.7 and 4.0 cm for targets at 15 and 30 m, respectively.

Internal resonance and energy transfer of a cable-stayed beam with a tuned mass damper

This study considers a novel nonlinear system, namely a cable-stayed beam with a tuned mass damper (cable-beam-TMD model), allowing the description of energy transfer among the beam, cable and TMD. In this system, the vibration of the TMD is involved and one-to-one-to-one internal resonance among the modes of the beam, cable and TMD is investigated when external primary resonance of the beam occurs. Galerkin’s method is utilized to discretize the equations of motion of the beam and cable. In this way, a set of ordinary differential equations are derived, which are solved by the method of multiple time scales. Then the steady-state solutions of the system are obtained by using Newton–Raphson method and continued by pseudo-arclength algorithm. The response curves, time histories and phase portraits are provided to explore the effect of the TMD on the nonlinear behaviors of the model. Meanwhile, a partially coupled system, namely a cable-beam-TMD model ignoring the vibration of the TMD, is also studied. The nonlinear characteristics of the two cases are compared with each other. The results reveal the occurrence of energy transfer among the beam, cable and TMD.

3T external phased-array magnetic resonance imaging in detection of obstetric anal sphincter lesions: a pilot study.

Three-dimensional endoanal ultrasound (3D EAUS) has been the gold standard for detecting anal sphincter lesions in patients with a history of obstetric anal sphincter injury (OASI). Advances in imaging technologies have facilitated the detection of these lesions with external phased-array magnetic resonance imaging (MRI), which could offer an alternative imaging modality for the diagnosis of residual OASI (ROASI) in centers where 3D EAUS imaging is not available. To compare two diagnostic modalities: the 3D EAUS and 3T external phased-array MRI in the detection of residual anal sphincter lesions. A total of 24 women with a history of OASI were imaged with both 3D EAUS and 3T external phased-array MRI after primary repair of the injury. Intraclass correlation (ICC) and interrater reliability (IRR) values were calculated for the grade and circumference of the sphincter lesion. Sphincter lesions were graded according to the Sultan classification. There was an almost perfect agreement between 3D EAUS and 3T external phased-array MRI in determining the extent of the sphincter lesions according to the Sultan classification (κ = 0.881; P < 0.001) and the circumference of the external anal sphincter defects, measured in degrees (κ = 0.896; P < 0.001). The results of this study indicate that 3T external phased-array MRI and 3D EAUS yield comparable results in the diagnosis of ROASI. These findings suggest that 3T external phased-array MRI could serve as an alternative diagnostic modality to 3D EAUS in the diagnosis of ROASI.

Evaluation of a robust dynamic vibration absorber based on negative stiffness and internal resonance against seismic excitation

In this study, a nonlinear absorber that works with a negative stiffness is introduced to control vibration and its effect on reducing earthquake damage is investigated. Negative stiffness increases structural softness and damping. Also, due to its inherent nonlinear nature, negative stiffness can cause internal resonance and transfer vibration energy from a directly excited vibrating mode to a higher frequency mode. Using these features can be effective in reducing vibration. First, to investigate the dynamic behavior in conditions without internal resonance and with 1:3 internal resonance, the proposed absorber is added to a nonlinear main system and when the system is under external resonance due to harmonic excitation, the negative stiffness parameter of the absorber for conditions with and without Internal resonance is adjusted. The mathematical model of the system is presented and the governing differential equations are derived. The governing equations are solved by the Multiple Scale method, the answers and their stability are examined, discussed and compared. Then, by generalizing the absorber ability to structures with general nonlinear behavior, the effect of the proposed absorber on reducing the damage caused by near and far from the fault earthquakes is studied by numerical simulation and for cases where under an earthquake record, The absorber intensifies the damage to the structure and loses its reliability, an active control loop is proposed and its effect is investigated.

Abstract 1657: Syngeneic tumor development, treatment responses and immune infiltrate in subcutaneous and orthotopic mouse models

Abstract Background: Syngeneic mouse tumor models are widely used and effective tools to evaluate efficacy of novel anti-cancer therapies. They are often implanted subcutaneously in a microenvironment that is unrelated to the site of origin. This can be problematic when evaluating immune modulating therapies as the tumor microenvironment is known to differ substantially between orthotopic and subcutaneous models. Here, we report the development and characterization of several syngeneic mouse tumor models implanted subcutaneously and orthotopically. The models are characterized by immune infiltrate and response to novel and conventional therapies. Methods: Murine MC38 (colon), TRAMPC1 (prostate) and GL261 (glioma) cell lines were implanted subcutaneously or orthotopically in immune competent mice. Tumor growth was monitored at multiple timepoints by external caliper measurements, magnetic resonance (MR) or ultrasound imaging. At confirmed tumor take, mice were treated with external radiation therapy (RT) or immune checkpoint inhibitors. Single cell suspensions were prepared from tumors and tumor draining lymph nodes (TdLNs) at various timepoints after treatment initiation and immuno-profiling was evaluated by multicolor flow cytometry. The tissues were analyzed for proportions of the following cell populations; CD4+ and CD8+ T lymphocytes, myeloid derived suppressor cells (MDSCs), NK cells and macrophages. Results: Subcutaneous and orthotopic tumor volumes developed at a similar pace. However, orthotopic tumor volumes estimated by MR imaging were detectable at earlier timepoints compared to subcutaneous volumes estimated by caliper measurements. Response to therapy was dependent on implantation site. This was further highlighted by the immune infiltration analysis, where CD4+ and CD8+ tumor infiltrating lymphocytes differed markedly between subcutaneous and orthotopic tumors. Also, the temporal profile of tumor infiltrating immune cells up to 14 days following therapy was established in the models. Conclusion: Subcutaneous and orthotopic versions of syngeneic mouse tumor models were successfully established and characterized with respect to their tumor immune microenvironment. The models displayed varying sensitivity towards RT and immune checkpoint inhibitors. Response to therapy was furthermore dependent on implantation site. Altogether, these advanced models are powerful tools for investigating treatment effect within preclinical immuno-oncology. Citation Format: Sigrid Cold, Saif AL-Haidar, Jennifer Solgaard Joergensen, Trine Bjoernbo Engel, Frederikke Petrine Fliedner, Lotte Kellemann Kristensen, Andreas Kjaer, Carsten Haagen Nielsen. Syngeneic tumor development, treatment responses and immune infiltrate in subcutaneous and orthotopic mouse models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1657.

Nonlinear Analysis of an Injection-Locked Oscillator Coupled to an External Resonator

This work investigates an injection-locked power oscillator inductively coupled to an external resonator for wireless power transfer. The system allows a high transfer efficiency, while ensuring a constant oscillation frequency versus the coupling factor, unlike free-running implementations. An analytical formulation provides insight into the impact of the coupling factor on the locked-operation ranges. Two types of qualitative behavior, delimited by a codimension-two bifurcation, are distinguished. The investigation is extended to a Class-E oscillator at 13.56 MHz, analyzed with a new harmonic balance (HB) method that provides the family of locked-solution curves in a single simulation. Very good agreement is obtained with the measurement results.

The role of cultural innovation in the success of luxury startups

AbstractLuxury startups' sensibility to the social and cultural environment is the dimension that in addition to the technical and strategic excellence and pricing strategy ensure the firms' long‐term success. Incorporating a humanities approach and design theory in the study of business challenges leads to articulated solutions. Luxury that is enduring, addresses the customer on a cognitive level and not solely on an emotional or physical one. A response to a startup's cultural context is the key to achieving internal consistency and (external) resonance with the consumers.

Including video and novel parameter-height of penetration of external anal sphincter-in magnetic resonance imaging reporting of anal fistula.

The main purpose of a radiologist’s expertise in evaluation of anal fistula magnetic resonance imaging (MRI) is to benefit patients by decreasing the incontinence rate and increasing the healing rate. Any loss of vital information during the transfer of this data from the radiologist to the operating surgeon is unwarranted and is best prevented. In this regard, two methods are suggested. First, a short video to be attached with the standardized written report highlighting the vital parameters of the fistula. This would ensure minimum loss of information when it is conveyed from the radiologist to the operating surgeon. Second, inclusion of a new parameter, the amount of external sphincter involvement by the anal fistula. This parameter is usually not included in the MRI report. This can be evaluated as the height of penetration of the external anal sphincter (HOPE) by the fistula. The external anal sphincter plays a pivotal role in maintaining continence. This parameter (HOPE) is distinct from the ‘height of internal opening’ and assumes immense importance as its knowledge is paramount to prevent damage to the external anal sphincter by the surgeon during surgery.

Stability of the Dynamical Motion of a Damped 3DOF Auto-parametric Pendulum System

PurposeThe motion of three degrees-of-freedom (DOF) of an automatic parametric pendulum attached with a damped system has been investigated. The kinematics equations of this system have been derived employing Lagrange’s equations in accordance to it’s the generalized coordinates.MethodsThe method of multiple scales (MMS) has been used to obtain the solutions of the controlling equations up to the third-order of approximation. The solvability criteria and modulation equations for primary external resonance have been explored simultaneously.ResultsThe non-linear stability approach has been used to analyze the stability of the considered system according to its different parameters. Time histories of the amplitudes and the phases of this system have been graphed to characterize the motion of the system at any given occurrence.ConclusionsThe different zones of stability and instability of this study have been checked and examined, in which the system's behavior has been revealed to be stable for various values of its variables.

Nonlinear Dynamics of an Oscillator Inductively Coupled to an External Resonator for Power Transfer and Data Transmission

This work presents an investigation of the nonlinear dynamics of an oscillator that is inductively coupled to an external resonator for power transfer applications. Analytical expressions are derived for the oscillation frequency and output power, which provide insight into the effect of the coupled resonator on the oscillator solution. From the analytical study, criteria are derived to maximize the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> range with a high efficiency and a limited variation of the oscillation frequency. The resistor of the external resonator can be modulated for data transmission to the core oscillator. Here the sensitivity to this resistor and its dependence on the coupling factor are analyzed in detail. The methods have been applied to a Class-E oscillator that has been analyzed through a contour-intersection technique. This is based on the extraction from harmonic balance (HB) of a bi-variate nonlinear admittance function accounting for the oscillator circuit, which is combined with the passive linear admittance function of the coupled resonator. The advantage is taken of the ease of this analysis to obtain constant-efficiency contours in the oscillatory regime, traced in the plane defined by the coupling factor and any suitable analysis parameter. By means of a bifurcation analysis, various phenomena, including the oscillation extinction plus onset versus the coupling factor and the appearance of quasi-periodic solutions, are detected and avoided. Very good correspondence has been obtained between simulation and measured results.

Integrated piezo-tribo hybrid acoustic-driven nanogenerator based on porous MWCNTs/PVDF-TrFE aerogel bulk with embedded PDMS tympanum structure for broadband sound energy harvesting

In this work, a novel type of acoustic-driven nanogenerator (ANG) that integrates piezoelectric and triboelectric effects is reported for broadband sound energy harvesting. With an internal structure combining beam-like porous multi-walled carbon nanotubes/polyvinylidene fluoride-trifluoroethylene (MWCNTs/PVDF-TrFE) aerogel and polydimethylsiloxane (PDMS) tympanum, the integrated MWCNTs/PVDF-TrFE/PDMS (MCPP) ANG achieves efficient collection of acoustic energy through the enhanced vibration and friction generated internally. Besides, by eliminating the need for a contact separation structure or an external resonator cavity, this design greatly simplifies the structure and contributes to the flexibility and durability of the device. The MCPP ANG, with 20 wt% sodium carboxymethyl cellulose (SCMC), 2 wt% MWCNTs and 5% w/v PDMS, reaches an optimal output of 34.4 V and 1.74 μA under 150 Hz and 115 dB sound stimulation, corresponding to an areal power density of 11.62 mW/m2. It possesses a broad working bandwidth from 110 Hz to 400 Hz, and can directly illuminate 7 light-emitting diodes (LEDs) in series. Employing a novel, simple and effective structural design, the ANG proposed here achieves flexible and stable acoustic collection, offering a promising path toward sound spectrum analysis, noise detection and power supply for various low-power sensors.